Competitions of magnetism and superconductivity in FeAs-based materials

You Wen-Longa, Gu Shi-Jiana, Lin Hai-Qinga, Yang Shuob

a Department of Physics and ITP, The Chinese
University of Hong Kong, Hong Kong, China; b Department of Physics and ITP, The Chinese
University of Hong Kong, Hong Kong, China;Institute of Theoretical Physics, Chinese Academy of
Sciences, Beijing 100190, China

Abstract Using the numerical unrestricted Hartree--Fock approach, we study
the ground state of a two-orbital model describing newly discovered
FeAs-based superconductors. We observe the competition of a (0,
π) mode spin-density wave and the superconductivity as the doping
concentration changes. There might be a small region in the
electron-doping side where the magnetism and superconductivity
coexist. The superconducting pairing is found to be spin singlet,
orbital even, and coexisting sxy + dx2-y2 wave (even
parity).